configure: remove unused checks

- for sys/uio.h
- for fork
- for connect

Ref: #11964

Closes #11973

configure.ac

@@ -3352,7 +3352,6 @@ AC_CHECK_HEADERS(
         sys/select.h \
         sys/socket.h \
         sys/ioctl.h \
-        sys/uio.h \
         unistd.h \
         stdlib.h \
         arpa/inet.h \
@@ -3536,7 +3535,6 @@ CURL_CHECK_FUNC_ALARM
 CURL_CHECK_FUNC_BASENAME
 CURL_CHECK_FUNC_CLOSESOCKET
 CURL_CHECK_FUNC_CLOSESOCKET_CAMEL
-CURL_CHECK_FUNC_CONNECT
 CURL_CHECK_FUNC_FCNTL
 CURL_CHECK_FUNC_FREEADDRINFO
 CURL_CHECK_FUNC_FSETXATTR
@@ -3588,7 +3586,6 @@ AC_CHECK_FUNCS([\
   arc4random \
   fchmod \
   fnmatch \
-  fork \
   fseeko \
   geteuid \
   getpass_r \

m4/curl-functions.m4

@@ -372,27 +372,6 @@ curl_includes_sys_types="\
 ])
 
 
-dnl CURL_INCLUDES_SYS_UIO
-dnl -------------------------------------------------
-dnl Set up variable with list of headers that must be
-dnl included when sys/uio.h is to be included.
-
-AC_DEFUN([CURL_INCLUDES_SYS_UIO], [
-curl_includes_sys_uio="\
-/* includes start */
-#ifdef HAVE_SYS_TYPES_H
-#  include <sys/types.h>
-#endif
-#ifdef HAVE_SYS_UIO_H
-#  include <sys/uio.h>
-#endif
-/* includes end */"
-  AC_CHECK_HEADERS(
-    sys/types.h sys/uio.h,
-    [], [], [$curl_includes_sys_uio])
-])
-
-
 dnl CURL_INCLUDES_SYS_XATTR
 dnl -------------------------------------------------
 dnl Set up variable with list of headers that must be
@@ -932,109 +911,6 @@ AC_DEFUN([CURL_CHECK_FUNC_CLOSESOCKET_CAMEL], [
   fi
 ])
 
-
-dnl CURL_CHECK_FUNC_CONNECT
-dnl -------------------------------------------------
-dnl Verify if connect is available, prototyped, and
-dnl can be compiled. If all of these are true, and
-dnl usage has not been previously disallowed with
-dnl shell variable curl_disallow_connect, then
-dnl HAVE_CONNECT will be defined.
-
-AC_DEFUN([CURL_CHECK_FUNC_CONNECT], [
-  AC_REQUIRE([CURL_INCLUDES_WINSOCK2])dnl
-  AC_REQUIRE([CURL_INCLUDES_SYS_SOCKET])dnl
-  AC_REQUIRE([CURL_INCLUDES_BSDSOCKET])dnl
-  AC_REQUIRE([CURL_INCLUDES_SOCKET])dnl
-  #
-  tst_links_connect="unknown"
-  tst_proto_connect="unknown"
-  tst_compi_connect="unknown"
-  tst_allow_connect="unknown"
-  #
-  AC_MSG_CHECKING([if connect can be linked])
-  AC_LINK_IFELSE([
-    AC_LANG_PROGRAM([[
-      $curl_includes_winsock2
-      $curl_includes_bsdsocket
-      $curl_includes_sys_socket
-      $curl_includes_socket
-    ]],[[
-      if(0 != connect(0, 0, 0))
-        return 1;
-    ]])
-  ],[
-    AC_MSG_RESULT([yes])
-    tst_links_connect="yes"
-  ],[
-    AC_MSG_RESULT([no])
-    tst_links_connect="no"
-  ])
-  #
-  if test "$tst_links_connect" = "yes"; then
-    AC_MSG_CHECKING([if connect is prototyped])
-    AC_EGREP_CPP([connect],[
-      $curl_includes_winsock2
-      $curl_includes_bsdsocket
-      $curl_includes_sys_socket
-      $curl_includes_socket
-    ],[
-      AC_MSG_RESULT([yes])
-      tst_proto_connect="yes"
-    ],[
-      AC_MSG_RESULT([no])
-      tst_proto_connect="no"
-    ])
-  fi
-  #
-  if test "$tst_proto_connect" = "yes"; then
-    AC_MSG_CHECKING([if connect is compilable])
-    AC_COMPILE_IFELSE([
-      AC_LANG_PROGRAM([[
-        $curl_includes_winsock2
-        $curl_includes_bsdsocket
-        $curl_includes_sys_socket
-        $curl_includes_socket
-      ]],[[
-        if(0 != connect(0, 0, 0))
-          return 1;
-      ]])
-    ],[
-      AC_MSG_RESULT([yes])
-      tst_compi_connect="yes"
-    ],[
-      AC_MSG_RESULT([no])
-      tst_compi_connect="no"
-    ])
-  fi
-  #
-  if test "$tst_compi_connect" = "yes"; then
-    AC_MSG_CHECKING([if connect usage allowed])
-    if test "x$curl_disallow_connect" != "xyes"; then
-      AC_MSG_RESULT([yes])
-      tst_allow_connect="yes"
-    else
-      AC_MSG_RESULT([no])
-      tst_allow_connect="no"
-    fi
-  fi
-  #
-  AC_MSG_CHECKING([if connect might be used])
-  if test "$tst_links_connect" = "yes" &&
-     test "$tst_proto_connect" = "yes" &&
-     test "$tst_compi_connect" = "yes" &&
-     test "$tst_allow_connect" = "yes"; then
-    AC_MSG_RESULT([yes])
-    AC_DEFINE_UNQUOTED(HAVE_CONNECT, 1,
-      [Define to 1 if you have the connect function.])
-    curl_cv_func_connect="yes"
-  else
-    AC_MSG_RESULT([no])
-    curl_cv_func_connect="no"
-  fi
-])
-
-
 dnl CURL_CHECK_FUNC_FCNTL
 dnl -------------------------------------------------
 dnl Verify if fcntl is available, prototyped, and